JP2016197354A - Power distribution circuit for solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power distribution circuit for solar cell, capable of distributing large power among solar cells of a photovoltaic power generation system in which a difference in power generation outputs is generated due to shade, and of smoothing steps occurring in current-voltage characteristics of the system to improve a power generation efficiency.SOLUTION: Surplus power of a solar cell M1 having a large power generation output is supplied via four switching elements S11-S14 repeating periodic ON/OFF operations and a capacitor C1 to a first coil L1 of a transformer T, and power induced by a second coil L2 of the transformer T is added to a power generation output of a solar cell 2 having a smaller power generation output via four switching elements S21-S24 repeating ON/OFF operations with a certain phase difference from the four switching elements S11-S14 and a capacitor C2. Thus, a step in the current-voltage characteristics of the system is smoothed.SELECTED DRAWING: Figure 1

Description

  The present invention improves the power generation efficiency of the entire system even when the installation environment of solar cells used in a solar power generation system is bad and part of it is shaded or when the output characteristics between solar cells vary. The present invention relates to a power distribution circuit that can be increased.

  Here, the term “solar cell” means a cluster in which bypass diodes are connected in parallel to both ends of a string of solar cells (photovoltaic elements) connected in series, and such a cluster is a single or Both solar cell modules configured by connecting in series are meant.

  The efficiency and the area of solar cells are increasing year by year, and solar cells with large power generation output are being developed. In a solar power generation system using such a large-capacity output solar cell, if the power generation output varies between individual solar cells, there is a possibility that the output of the entire system is greatly reduced. Such variations in the power generation output between solar cells are caused by shaded or aged output reduction that occurs in some solar cells.

  FIG. 21 is a diagram schematically showing a solar power generation system composed of two solar cells M1 and M2 connected in series. These solar cells M1 and M2 are of the same specification. Yes.

  Further, bypass diodes BD1 and BD2 are connected between the positive terminal P1 and the negative terminal P2 of the solar cells M1 and M2, respectively, and the positive terminal P1 of the solar cell M1 and the negative terminal P2 of the solar cell M2 are respectively connected. The output is connected to an external load such as a power conditioner via an output electric circuit A.

  When these solar cells M1 and M2 are both installed in the sun and are exposed to sufficient sunlight, the external output that combines them is as shown by the thick solid line in FIG. Current / voltage characteristics with the maximum output operating point as Pm are shown.

  However, for example, when one solar cell M2 enters the shade, the power generation output on the side of the solar cell M2 decreases and shows a step-like current-voltage characteristic as indicated by a thick solid line in FIG. . In the figure, the sum of the areas of the region (1) and the region (3) represents the power generation output (maximum value) of the solar cell M1, and the area of the region (2) is the power generation output of the solar cell M2. (Maximum value).

  In such current / voltage characteristics, the power generation output obtained when the maximum output operating point Pm is at the position shown in the figure is the sum of the areas of the areas (1) and (2), and is indicated by hatching. The part (3) is a loss because it cannot contribute to the power generation output.

  On the other hand, conventionally, as described in Patent Document 1, a solar power generation system using an AC solar cell module in which a micro inverter is mounted on each solar cell module has been proposed.

  Such a system is a solar cell module that performs maximum power follow-up (MPPT) control on each solar cell module and performs DC / AC conversion of its output, and is said to have little loss due to shade or the like. .

  However, since the AC solar cell module has a complicated conversion circuit, the manufacturing cost of each solar cell module is increased, and since the conversion operation is always performed, conversion loss occurs even in the absence of shade. In addition, when the conversion circuit breaks down, the solar cell module on which the conversion circuit is mounted cannot be used, so there is a problem in reliability.

  Therefore, the inventor of the present application solves the above-described problems and improves the reduction in power generation efficiency of the entire system due to variations in power generation output between solar cells. A power distribution circuit was proposed.

  The power distribution circuit described in Patent Document 2 is mainly composed of a simple and low-energy-loss circuit consisting of a switching element such as an inductor, a transistor or a relay, and a smoothing circuit using a smoothing capacitor or a low-pass filter. The current of the entire photovoltaic power generation system is distributed by allocating a part of the power generation output from the solar cell side where the power generation output is large to the solar cell side where the power generation output is small between the adjacent solar cells connected in series.・ Improve voltage characteristics.

  When the power distribution circuit is incorporated in the system shown in FIG. 21, the curve indicating the current-voltage characteristics of the entire system before operating the power distribution circuit is when the power generation output on the solar cell M2 side is reduced. As shown by a broken line in FIG. 24, the maximum output operating point has a stepped shape with Pm. By operating this power distribution circuit, a part (3) ′ of the power generation output of the solar cell M1 is obtained. It is distributed to the solar cell M2 side and added to the power generation output (2).

  The area of the region (3 ′) is approximately half the area of the region (3) where the power generation output of the solar cell M1 shown in FIG. 23 cannot be used. By allocating from the battery M1 side to the solar cell M2 side, the current-voltage characteristic of the entire system is improved to a smoothed characteristic in which the maximum power operating point indicated by a thick solid line in FIG. Efficiency is improved.

JP 11-318042 A JP 2014-103766 A

  The power distribution circuit for solar cells proposed in Patent Document 2 described above has the advantage that the loss of the circuit itself is small, the circuit configuration is simple and can be reduced in size, and if a failure occurs in the circuit. However, since the photovoltaic power generation system itself does not fall out of use, it has high reliability.

  However, in recent years, since the capacity of individual solar cells constituting the system has increased, the conventional power distribution circuit as described above has a sufficient effect because the power distributed between the solar cells is insufficient. It may not be obtained.

  Therefore, the present invention solves the problems in the prior art as described above, and can distribute a large amount of power between solar cells of a photovoltaic power generation system in which a difference in power generation output occurs due to shade or the like. An object of the present invention is to provide a power distribution circuit for a solar cell that can smooth a step appearing in voltage characteristics and improve power generation efficiency.

  The power distribution circuit according to the present invention provided for the above-described purpose includes a plurality of solar cells connected in series with each other, with bypass diodes connected in parallel and connected in series to an external load. A power distribution circuit provided, the first charge / discharge path that is electrically connected to the positive terminal of the preceding solar cell, the second charge / discharge path that is electrically connected to the negative terminal of the preceding solar battery, and the subsequent solar A third charging / discharging path that conducts with the positive electrode terminal of the battery, a fourth charging / discharging path that conducts with the negative electrode terminal of the subsequent solar battery, one end connected to the first charging / discharging path, and the other The first communication circuit, one end of which is connected to the second charge / discharge path, one end is connected to the first charge / discharge path, and the other end is connected to the second charge / discharge path, The second communication circuit, one end is connected to the third charge / discharge path, and the other end is the fourth charge / discharge A fourth communication circuit, one end connected to the third charge / discharge path, and the other end connected to the fourth charge / discharge path, and Next to the connection point with the first charging / discharging path, the first switching element and the first connection circuit with the second charging / discharging path adjacent to the connection point with the second charging / discharging path Embedded in the second switching element and the second communication circuit, adjacent to the connection point of the first charging / discharging path, and the third switching element and the second connection circuit. The fourth switching element incorporated adjacent to the connection point with the second charge / discharge path and the third connection electrical circuit incorporated adjacent to the connection point with the third charge / discharge path. The fifth switching element and the third communication circuit are incorporated adjacent to the connection point with the fourth charge / discharge path, The fourth switching circuit and the fourth connection circuit are incorporated next to the connection point of the third charge and discharge path, and the seventh switching element and the fourth connection circuit are connected to the fourth charge and discharge path. And an eighth switching element incorporated adjacent to the connection point between the first switching element and one end of the eighth switching element connected to the first communication circuit between the first switching element and the second switching element. A first winding connected to the second communication circuit between the third switching element and the fourth switching element, and a magnetically coupled to the winding, and one end of the first winding is the fifth switching The second winding is connected to the third communication circuit between the element and the sixth switching element, and the other end is connected to the fourth communication circuit between the seventh switching element and the eighth switching element. Transformer with 1: 1 winding ratio with wire and first charge / discharge A first capacitor connected across the electrical path and the second charge / discharge path, a second capacitor connected across the third charge / discharge path and the fourth charge / discharge path, and the previous stage The first voltage sensor that detects the output voltage of the solar cell, the second voltage sensor that detects the output voltage of the subsequent solar cell, and the ON / OFF operation of the respective switching elements in a common cycle And a switching control circuit to be repeated.

  In the switching control circuit, the first and fourth switching element sets and the second and third switching element sets have the same phase in each set, and the opposite phases between these sets. The group of the fifth and eighth switching elements and the group of the sixth and seventh switching elements are operated in the same phase within each group, and each switching element is turned on / off with an opposite phase between these groups. At the same time, when the detection value of the first voltage sensor is larger than the detection value of the second voltage sensor, switching consisting of a set of the first and fourth switching elements and a set of the second and third switching elements. The ON / OFF operation timing of the element group is set to be higher than the ON / OFF operation timing of the switching element group including the fifth and eighth switching element groups and the sixth and seventh switching element groups. Phase angle δ (where 0 <δ <π), and when the detection value of the second voltage sensor is larger than the detection value of the first voltage sensor, the fifth and eighth switching elements The ON / OFF operation timing of the switching element group consisting of the set of No. 6 and the set of the sixth and seventh switching elements consists of the set of the first and fourth switching elements and the set of the second and third switching elements. It is characterized in that the phase is advanced by a predetermined phase angle δ (where 0 <δ <π) with respect to the timing of the ON / OFF operation of the switching element group.

In the power distribution circuit of the present invention, the switching control circuit includes the first winding and the second winding of the transformer represented by the following formula based on the detection values of the first voltage sensor and the second voltage sensor. It is desirable to include a calculation unit that calculates the phase angle δ that maximizes the moving power P delivered between the windings.
P = (V1V2 / ωLs) · δ (1-δ / π)

  Here, V1 is the output voltage of the former solar cell detected by the first voltage sensor, V2 is the output voltage of the latter solar cell detected by the second voltage sensor, and ω is the output voltage of each switching element. The angular frequency of the ON / OFF operation, Ls, represents the leakage inductance of the transformer.

  According to the first aspect of the present invention, when the power generation output varies between the solar cells used in the photovoltaic power generation system due to shade, dirt on the light receiving surface, aging deterioration, etc. Power can be distributed in a balanced manner between batteries.

As a result, the difference in the current-voltage characteristics of the entire photovoltaic power generation system is smoothed, and the power that was originally lost cannot be used and the lost power can be used. Can do.
In addition, since the step of the current-voltage characteristic is smoothed, the maximum output operating point of the power conditioner can be easily detected, and MPPT mismatch loss can be avoided.

  The main part of the power distribution circuit of the present invention is composed of switching elements such as relays and FETs (field effect transistors), transformers, capacitors, etc., and has a simple structure and DAB (Dual Active Bridge). Since the principle of the bidirectional DC-DC converter is applied, it is possible to distribute a large amount of power among solar cells having a difference in power generation output, and a solar cell having a large power generation capacity in recent years It can correspond to.

  In addition, in the system using the conventional AC solar cell module, even when there is no shade, circuit loss due to AC / DC conversion always occurs, whereas the power distribution circuit according to the present invention has no shade. Can stop its operation and prevent the power generation efficiency from being reduced due to circuit loss.

  Furthermore, in the solar power generation system using the conventional AC solar cell module, when the micro inverter mounted on the solar cell module fails, the solar cell module itself becomes unusable, but in the power distribution circuit of the present invention, Even if a failure occurs and its function stops, there is no possibility that the function of the photovoltaic power generation system itself will be disturbed.

  According to the invention described in claim 2, the switching control circuit constituting a part of the power distribution circuit controls the operation of each switching element so that the power distributed between the solar cells is maximized. Since it has the function, the power generation efficiency of the entire photovoltaic power generation system can be increased as much as possible.

It is a schematic diagram of the photovoltaic power generation system which consists of two solar cells M1 and M2 connected in series, showing one embodiment of the power distribution circuit of the present invention. It is a block diagram of a switching control circuit in one embodiment of a power distribution circuit of the present invention. When the power generation output of the solar cell M1 is larger than the power generation output of the solar cell M2, the output voltage V1 of each solar cell M1, M2 during the maximum output operation of the system before and during the operation of the power distribution circuit of the present invention, It is a figure showing V2, respectively. 6 is a timing chart showing ON / OFF operation of each switching element and a change in current flowing through a transformer when the power distribution circuit is operating when the power generation output of the solar cell M1 is larger than the power generation output of the solar cell M2. FIG. 5 is a diagram schematically illustrating a path of a current flowing through the power distribution circuit of the present invention in STEP 1 of FIG. 4. FIG. 5 is a diagram schematically illustrating a path of a current flowing through the power distribution circuit of the present invention in STEP 2 of FIG. 4. FIG. 5 is a diagram schematically illustrating a path of a current flowing through the power distribution circuit of the present invention in STEP 3 of FIG. 4. FIG. 5 is a diagram schematically illustrating a path of a current flowing through the power distribution circuit of the present invention in STEP 4 of FIG. 4. It is a figure which illustrates typically the course of the current which flows through the power distribution circuit of the present invention in STEP5 of FIG. FIG. 5 is a diagram schematically illustrating a path of a current flowing through the power distribution circuit of the present invention in STEP 6 of FIG. 4. 5 is a timing chart showing ON / OFF operation of each switching element and a change in current flowing through a transformer when the power distribution circuit is operating when the power generation output of the solar cell M2 is larger than the power generation output of the solar cell M1. It is a figure which illustrates typically the course of the current which flows through the power distribution circuit of the present invention in STEP1 of FIG. It is a figure which illustrates typically the course of the current which flows through the power distribution circuit of the present invention in STEP2 of FIG. It is a figure which illustrates typically the course of the current which flows through the power distribution circuit of the present invention in STEP3 of FIG. It is a figure which illustrates typically the course of the current which flows through the power distribution circuit of the present invention in STEP4 of FIG. It is a figure which illustrates typically the course of the current which flows through the power distribution circuit of the present invention in STEP5 of FIG. It is a figure which illustrates typically the course of the current which flows through the power distribution circuit of the present invention in STEP6 of FIG. It is a graph which shows the relationship between the electric power P which moves via a transformer, and phase angle (delta). It is a flowchart explaining operation | movement of a switching control circuit. It is a schematic diagram of the photovoltaic power generation system which consists of the three solar cells M1, M2, and M3 connected in series which shows another embodiment of the power distribution circuit of this invention. It is a figure which shows typically the solar energy power generation system which consists of two solar cells M1, M2. It is a figure which shows the current-voltage characteristic in case both solar cells are in the sun. It is a figure which shows the current-voltage characteristic when one solar cell enters the shade. It is a figure which shows the current-voltage characteristic improved by incorporating a power distribution circuit.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment shown in FIG. 1 shows an example in which the power distribution circuit 1 of the present invention is incorporated in a solar power generation system configured by two solar cells M1 and M2 connected in series to an external load. .

  As shown in the figure, the positive terminal P1 of the solar cell M1 and the negative terminal P2 of the solar cell M2 are connected to an external load such as a power conditioner via the output electric circuit A, and the negative electrode of the solar cell M1. The terminal P2 and the positive terminal P1 of the solar cell M2 are connected by a connecting electric circuit B. Further, bypass diodes BD1 and BD2 are connected between the positive terminal P1 and the negative terminal P2 of the solar cells M1 and M2, respectively.

  In the following description, the front and rear directions of these solar cells M1 and M2 are respectively the positive terminal P1 side as the front side and the negative terminal P2 side as the rear side, M1 as the front solar cell, and M2 as the rear solar cell. And

  The power distribution circuit 1 of the present invention includes a charge / discharge path 2 (first charge / discharge path) that conducts to a positive electrode terminal P1 of the preceding stage solar cell M1 via a connection point j1 on the output circuit A, and the solar cell. The negative electrode terminal P2 of M1 has a charging / discharging path 3 (second charging / discharging path) that conducts through a connection point j2 on the connection circuit B.

  In addition, the power distribution circuit 1 includes a charge / discharge path 4 (third charge / discharge path) that conducts to the positive electrode terminal P1 of the subsequent solar battery M2 via a connection point j3 on the connection circuit B, and the solar battery. The negative electrode terminal P2 of M2 has a charging / discharging path 5 (fourth charging / discharging path) that conducts through a connection point j4 on the output electric path A.

  The charging / discharging path 2 and the charging / discharging path 3 are connected to each other via a connecting electric circuit 6 (first connecting electric circuit) and a connecting electric circuit 7 (second connecting electric circuit). Further, the charging / discharging path 4 and the charging / discharging path 5 are communicated with each other via a connecting electric circuit 8 (third connecting electric circuit) and a connecting electric circuit 9 (fourth connecting electric circuit).

  A switching element S11 (first switching element) is incorporated in the communication circuit 6 adjacent to the connection point j5 with the charging / discharging path 2, and adjacent to the connection point j6 with the charging / discharging path 3. The switching element S12 (second switching element) is incorporated.

  In addition, a switching element S13 (third switching element) is incorporated in the connection electrical path 7 adjacent to the connection point j7 with the charge / discharge path 2, and adjacent to the connection point j8 with the charge / discharge path 3. Thus, a switching element S14 (fourth switching element) is incorporated.

  Further, the connection circuit path 8 incorporates a switching element S21 (fifth switching element) adjacent to the connection point j9 with the charge / discharge path 4 and is adjacent to the connection point j10 with the charge / discharge path 5. Thus, the switching element S22 (sixth switching element) is incorporated.

  In addition, a switching element S23 (seventh switching element) is incorporated in the connection electrical path 9 adjacent to the connection point j11 with the charge / discharge path 4 and adjacent to the connection point j12 with the charge / discharge path 5. Thus, the switching element S24 (eighth switching element) is incorporated.

  In the power distribution circuit 1 of the present embodiment, transistors (FETs) are used as the switching elements S11 to S24. In addition, you may use a relay for these switching elements.

  A connection point j13 between the switching element S11 and the switching element S12 on the connection circuit 6 and a connection point j14 between the switching element S13 and the switching element S14 on the connection circuit 7 are respectively connected to the winding L1 (first first) of the transformer T. Both ends of the winding are connected.

  Further, the connection point j15 between the switching element S21 and the switching element S22 on the communication circuit 8 and the connection point j16 between the switching element S23 and the switching element S24 on the connection circuit 9 are respectively connected to the winding L2 (first) of the transformer T. Both ends of the second winding) are connected.

  Note that one of the two windings L1 and L2 constitutes the primary side winding of the transformer T, and the other constitutes the secondary side winding. In FIG. Transformers T are displayed on both the line L1 side and the winding L2 side, and these represent the same one. The winding ratio between the windings L1 and L2 is 1: 1.

  In addition, a capacitor C1 (first capacitor) is connected across the connection point j17 on the charge / discharge path 2 and the connection point j18 on the charge / discharge path 3. A capacitor C2 (second capacitor) is connected across the connection point j19 on the charge / discharge path 4 and the connection point j20 on the charge / discharge path 5.

  Between the connection point j21 adjacent to the connection point j1 on the charge / discharge path 2 and the connection point j22 adjacent to the connection point j2 on the charge / discharge path 3, the positive terminal P1 and the negative terminal of the solar cell M1 in the previous stage A voltage sensor VS1 (first voltage sensor) for detecting a voltage between P2 is connected.

  Between the connection point j23 adjacent to the connection point j3 on the charge / discharge path 4 and the connection point j24 adjacent to the connection point j4 on the charge / discharge path 5, the positive electrode terminal P1 of the solar cell M2 in the subsequent stage is connected. A voltage sensor VS2 (second voltage sensor) for detecting the voltage between the negative terminals P2 is incorporated.

  Furthermore, between the charging / discharging path 2 and the charging / discharging path 3, while reducing the switching noise which each switching element S11-S14 generate | occur | produces, in order to smooth the fluctuation | variation of the electric current which flows through these charging / discharging paths 2 and 3 A low-pass filter LPF1 is incorporated.

  Moreover, between the charging / discharging path 4 and the charging / discharging path 5, while removing the switching noise which each switching element S21-S24 generate | occur | produces, the fluctuation | variation of the electric current which flows through these charging / discharging paths 4 and 5 is smoothed A low-pass filter LPF2 is incorporated. The low-pass filters LPF1 and LPF2 can operate the power distribution circuit 1 even if omitted, but it is desirable to use them in practice.

  Although not shown in FIG. 1, the power distribution circuit 1 includes a switching control circuit for controlling the ON / OFF switching operation of the switching elements S11 to S24. FIG. 2 is a block diagram of the switching control circuit. As shown in FIG. 2, the switching control circuit 10 generates a common pulse signal that serves as a reference for the ON / OFF timing of the switching elements S11 to S24. It has a pulse oscillator.

  The pulse signal output from the pulse oscillator is input to the phase controller. The phase control unit generates two pulse signals having a phase difference from the pulse signal, and transmits one of them to the complementary circuit CP1 and the other to the complementary circuit CP2.

  The complementary circuit CP1 outputs pulse signals having opposite phases to the driver circuit D11 and the driver circuit D12 based on the pulse signal sent from the phase control unit. Based on the pulse signal sent from the complementary circuit CP1, the driver circuit D11 periodically performs ON / OFF operations of the switching element S11 and the switching element S14 in the same phase.

  Based on the pulse signal sent from the complementary circuit CP1, the driver circuit D12 causes the switching element S12 and the switching element S13 to periodically perform ON / OFF operations in the same phase. Further, since the operations of the driver circuit D11 and the driver circuit D12 are made complementary by the complementary circuit CP1, the pair of the switching element S11 and the switching element S14 and the pair of the switching element S12 and the switching element S13 are in opposite phases. ON / OFF operation is performed.

  The complementary circuit CP2 outputs pulse signals having opposite phases to the driver circuit D21 and the driver circuit D22 based on the pulse signal sent from the phase control unit. Based on the pulse signal sent from the complementary circuit CP2, the driver circuit D21 causes the switching element S21 and the switching element S24 to periodically perform ON / OFF operations in the same phase.

  Based on the pulse signal sent from the complementary circuit CP2, the driver circuit D22 causes the switching element S22 and the switching element S23 to periodically perform ON / OFF operations in the same phase. Further, since the operations of the driver circuit D21 and the driver circuit D22 are complemented by the complementary circuit CP2, the pair of the switching element S21 and the switching element S24 and the pair of the switching element S22 and the switching element S23 are in opposite phases. ON / OFF operation is performed.

  Furthermore, from the group of switching elements S11 and S14, the group of switching elements consisting of the group of switching elements S12 and S13, the group of switching elements S21 and S24, and the group of switching elements S22 and S23 A time difference is provided in the operation timing by the phase difference controlled by the phase control unit.

  The phase difference controlled by the phase control unit is calculated based on voltage values detected by the two voltage sensors VS1 and VS2 by the calculation unit. The arithmetic unit also performs ON / OFF control of energization to the driver circuits D11 to D22. Details of the operation of the switching control circuit 10 will be described later.

  In the present embodiment, the calculation unit is constituted by a microcomputer, and the operations of all the switching elements S11 to S24 are controlled in accordance with a program incorporated therein. Note that the entire switching control circuit may be configured by a single microcomputer.

Next, the operation of the power distribution circuit 1 configured as described above will be described.
In the system shown in FIG. 1, when the power generation output of the solar cell M1 at the front stage is larger than the power generation output of the solar battery M2 at the rear stage, all the switching elements S11 to S24 are turned off as shown in FIG. In this state, the system exhibits a step-like current-voltage characteristic with the maximum output operating point as Pm, as shown by a solid line in FIG.

  In addition, the curve shown with the broken line in the figure represents the current-voltage characteristic of only the solar cell M1, and at the maximum output operating point Pm, the solar cell M1 itself operates at the point a on the broken line. , V1a represents the output voltage of the solar cell M1. The point Pm, the point a, and the difference V2a represent the output voltage of the solar cell M2, and V1a> V2a.

  In this state, the power distribution circuit 1 is activated, and the switching control circuit 10 periodically repeats the ON / OFF switching operation of each switching element at the timing shown in FIG. In the figure, the hatched portion indicates that the switching element is ON, and the horizontal axis indicates the pulse oscillator in the switching control circuit 10 shown in FIG. It is indicated by ωt multiplied by the angular frequency ω.

  As shown in FIG. 4, the switching element S11 and switching element S14 group and the switching element S12 and switching element S13 group synchronize ON / OFF operation within each group, and the ON / OFF between these groups. The operation is performed in a complementary manner with opposite phases.

  In addition, the ON / OFF operation of the group of the switching element S21 and the switching element 24 and the group of the switching element 22 and the switching element S23 are synchronized in each group, and the ON / OFF operation is in reverse phase between these groups. Complementary.

  At this time, the periodic ON / OFF operation timing of the switching element group including the switching element S11 and the switching element S14 and the switching element S12 and the switching element S13 is set as follows. The switching element group consisting of the combination of the switching element 22 and the switching element S23 is advanced by a predetermined phase angle δ (where 0 <δ <π).

  Due to the periodic ON / OFF operation of the four switching elements S11 to S14, a part of the output current of the solar cell M1 is converted into a periodically changing current It1 indicated by a solid line in FIG. It flows in one winding L1 of the transformer T.

  Accordingly, a current It2 indicated by a broken line in FIG. 4 is induced in the other winding L2 of the transformer T in the direction opposite to the current flowing through the winding L1, and this current It2 is the solar cell M2. The four switching elements S21 to S24 on the side are rectified into a direct current by a periodic ON / OFF operation.

  This current is added to the output current of the solar cell M2 when flowing from the charging / discharging path 4 to the connection circuit B at the connection point j3, and the output current of the solar cell M2 flowing to the preceding stage solar cell M1 connected in series. The shortage is replenished. On the other hand, the surplus current flowing from the external load to the solar cell M2 is detoured to the charge / discharge path 5 side at the connection point j4.

  It should be noted that currents It1 and It2 shown in FIG. 4 indicate states after a sufficient time has passed since the power distribution circuit 1 was started and the steady operation state has been entered. The currents It1 and It2 Changes symmetrically in the forward / reverse direction (vertical direction in the figure) over time.

  Hereinafter, the operation of the power distribution circuit 1 in the steady operation state is performed in six sections of STEP1 to STEP6 in one cycle of the change of the current It1 flowing in the winding L1 of the transformer T (current It2 flowing in the winding L2). This will be described in detail separately.

  As shown in FIG. 4, STEP1 is a period from when the current It1 flowing through the winding L1 of the transformer T increases from 0 ampere until the switching elements S21 and S24 are turned on and the switching elements S22 and S23 are turned off.

  STEP2 is a period from the end of STEP1 until the switching elements S11 and S14 are turned off and the switching elements S12 and S13 are turned on. STEP3 is a period from the end of STEP2 until the current It1 decreases to 0 amperes.

  STEP4 is a period from the end of STEP3 until the switching elements S21 and S24 are turned off and the switching elements S22 and S23 are turned on. STEP5 is a period from the end of STEP4 until the switching elements S11 and S14 are turned on and the switching elements S12 and S13 are turned off.

  STEP 6 is a period from the end of STEP 5 until the current It1 flowing in the opposite direction decreases to 0 amperes. In STEP 6 and subsequent steps, the operation is repeated from STEP 1 again.

FIG. 5 is a diagram schematically illustrating the flow of current in the power distribution circuit 1 in STEP 1. The broken line with an arrow in the drawing represents the current flowing in the power distribution circuit 1.
In addition, in each figure explaining the current flow in the subsequent power distribution circuit 1 including the figure, the low-pass filters LPF1 and LPF2 and the voltage sensors VS1 and VS2 in FIG. 1 are shown for easy understanding of the current path. Is omitted.

In the figure, Ia represents the current flowing in and out of the charge / discharge path 2 and charge / discharge path 3 with respect to the power distribution circuit 1, Ib represents the current flowing in and out of the charge / discharge path 4 and charge / discharge path 5, and the current flowing through the capacitor C1. Ic and the current flowing through the capacitor C2 are denoted by Id.
Furthermore, the direction in which the currents It1 and It2 flow is defined as the forward direction in which the currents It1 and It2 respectively pass through the windings L1 and L2 in the right direction.

  As shown in FIG. 4, in STEP1, the switching elements S11 and S14 are ON, the current It1 monotonously increases in the forward direction, and the current It2 monotonously increases in the reverse direction.

  As shown in FIG. 5, in STEP1, the current Ia flows from the positive terminal P1 of the solar cell M1 to the charge / discharge path 2 through the connection point j1. A part of the current Ia is shunted from the connection point j17 to the capacitor C1 as the current Ic and charged, and the rest is wound as the current It1 from the charging / discharging path 2 side via the connection point j5 to the winding of the transformer T. It flows through the line L1 and further flows from the connection point j8 to the charge / discharge path 3 side.

  Further, in STEP1, the current It1 that has passed through the winding L1 merges with the current Ic that flows through the capacitor C1 at the connection point j18 to become the current Ia and flows through the charge / discharge path 3, and from the connection point j2 via the connection circuit B. Flows to the negative terminal P2 of the solar cell M1.

  On the other hand, since the switching elements S22 and S23 are ON, as shown in FIG. 4, a current It2 that increases in the opposite direction to the current It1 is induced in the other winding L2 of the transformer T. This current It2 flows through the winding L2 from the charge / discharge path 4 side via the connection point j11, and further flows from the connection point j10 to the charge / discharge path 5 side.

  In STEP 1, the capacitor C 2 is discharged, and the discharge current Id is divided into a current It 2 flowing to the winding L 2 and a current Ib flowing through the charge / discharge path 4 at a connection point j 19 with the charge / discharge path 4. The current Ib is added to the output current of the solar cell M2 at the connection point j3, and flows to the negative terminal P2 of the preceding solar cell M1 via the connection circuit B.

  On the other hand, the current Ib flows into the charging / discharging path 5 from the output electric circuit A connected to the external load via the connection point j4. The current Ib is merged with the current It2 at the connection point j20 and flows into the capacitor C2. .

  As shown in FIG. 6, in STEP2, the switching elements S11 and S14 are ON, the switching elements S12 and S13 are OFF, and the current flows from the positive terminal P1 of the solar cell M1 to the charge / discharge path 2 via the connection point j1. Ia flows in, merges with the discharge current Ic of the capacitor C1 at the connection point j17, and flows through the winding L1 as a current It1.

  The current It1 further flows into the charging / discharging path 3 at the connection point j8, is shunted at the connection point j18, a part of which flows as the current Ic to the capacitor C1, and the remainder passes through the connection point j2 to the solar cell M1. Flows to the negative terminal P2. Note that, as shown in FIG. 4, in STEP2, the current It1 gradually decreases.

  On the other hand, in STEP2, the switching elements S21 and S24 are ON, and the switching elements S22 and S23 are OFF. As shown in FIG. 6, a current It2 is induced in the winding L2 in the direction opposite to the current It1.

  This current It2 flows through the charging / discharging path 4 from the connection point j9, and at the connection point j19, a part thereof flows into the capacitor C2 as the current Id and charges it, and the rest as the current Ib at the connection point j3. And flows to the negative terminal P2 of the preceding solar cell M1 via the connecting electric circuit B.

  On the other hand, the current Ib flows through the charge / discharge path 5 from the external load side via the connection point j4 with the output electric circuit A. The current Ib is added with the current Id flowing through the capacitor C2 at the connection point j20 and flows to the winding L2 as the current It2.

  Next, in STEP3, the switching elements S12, S13 are ON and the switching elements S11, S14 are OFF, and the current It1 flows in the forward direction while decreasing in the winding L1, as shown in FIG.

  As shown in FIG. 7, the current It1 flows from the charge / discharge path 3 side via the connection point j6 through the winding L1 to the charge / discharge path 2 side via the connection point j7. Is connected to the current Ia flowing into the charge / discharge path 2 from the positive electrode terminal P1 of the solar cell M1 via the connection point j1, and flows into the capacitor C1 as the current Ic to be charged.

  The current Ic is further shunted into a current It1 that goes to the winding L1 at the connection point j18 and a current Ia that flows from the charge / discharge path 3 to the negative terminal P2 of the solar cell M1 via the connection circuit B at the connection point j2.

  In STEP 3, the switching elements S21 and S24 are ON and the switching elements S22 and S23 are OFF, and the current It2 induced in the winding L2 flows in the reverse direction while decreasing as shown in FIG.

  The current It2 flows from the charge / discharge path 5 side via the connection point j12 through the winding L2 to the charge / discharge path 2 side via the connection point j9, and is discharged from the capacitor C2 at the connection point j19. The current Ib is merged with Id, and is added to the current flowing through the solar cell M2 from the charging / discharging path 4 at the connection point j3 and flows to the negative terminal P2 of the solar cell M1.

  On the other hand, in the charge / discharge path 5, a part of the current flowing from the external load through the output circuit A flows as the current Ib from the connection point j4, and the current Id flowing to the capacitor C2 and the current It2 flowing to the winding L2 at the connection point j20. Divide into

  In STEP4, the switching elements S12 and S13 are ON and the switching elements S11 and S14 are OFF. As shown in FIG. 8, the current It1 reverses the winding L1 via the connection point j7 from the charge / discharge path 2 side. In the direction and further from the connection point j6 to the charge / discharge path 3 side.

  Further, the switching elements S21 and S24 are ON, the switching elements S22 and S23 are OFF, and the current It2 induced in the winding L2 passes through the winding L2 from the charge / discharge path 4 side via the connection point j9. And then flows from the connection point j12 to the charge / discharge path 5 side.

  As shown in FIG. 4, in STEP 4, the direction of the current It1 with respect to the winding L1 and the direction of the current It2 with respect to the winding L2 are opposite to those in STEP1, but the other current flows are the same as in STEP1. is there.

  In STEP5, the switching elements S11 and S14 are OFF and the switching elements S12 and S13 are ON. As shown in FIG. 9, the current It1 reverses the winding L1 via the connection point j7 from the charge / discharge path 2 side. In the direction and further from the connection point j6 to the charge / discharge path 3 side.

  Further, the switching elements S21 and S24 are OFF, the switching elements S22 and S23 are ON, and the current It2 induced in the winding L2 is forward from the charging / discharging path 5 via the connection point j10. And then flows from the connection point j11 to the charge / discharge path 4 side.

  As shown in FIG. 4, in STEP 5, the direction of the current It1 with respect to the winding L1 and the direction of the current It2 with respect to the winding L2 are opposite to those in STEP2, but the other current flows are the same as in STEP2. is there.

  In STEP6, the switching elements S11 and S14 are ON, and the switching elements S12 and S13 are OFF. As shown in FIG. 10, the current It1 flows through the winding L1 in the reverse direction via the connection point j8 from the charge / discharge path 3 side. And further flows from the connection point j5 to the charge / discharge path 2 side.

  Further, the switching elements S21 and S24 are OFF, the switching elements S22 and S23 are ON, and the current It2 induced in the winding L2 is forward from the charging / discharging path 5 via the connection point j10. And then flows from the connection point j11 to the charge / discharge path 4 side.

  As shown in FIG. 4, in STEP 6, the direction of the current It1 with respect to the winding L1 and the direction of the current It2 with respect to the winding L2 are opposite to those in STEP3, but the other current flows are the same as in STEP3. is there.

  As described above, when the generated power of the solar cell M1 at the front stage is larger than the power generation output of the solar battery M2 at the rear stage, the current Ib flowing through the charge / discharge path 4 of the power distribution circuit 1 is as shown in STEP1 to STEP6. Since it is added to the output current of the solar cell M2 in each period, the maximum output operating point P′m is moved and the current-voltage characteristic is smoothed as shown by the one-dot chain line in FIG. Improved.

  Next, in the system shown in FIG. 1, when the generated power of the subsequent solar cell M2 is larger than the generated output of the preceding solar cell M1, the switching elements S11 to S24 are turned on / off according to the timing chart of FIG. Performs an OFF operation.

  As shown in the figure, in this case, contrary to the case of FIG. 4 described above, the periodicity of the switching element group composed of the combination of the switching element S21 and the switching element 24 and the combination of the switching element 22 and the switching element S23. The timing of the ON / OFF operation is advanced by a phase angle δ with respect to the switching element group including the switching element S11 and the switching element S14 and the switching element S12 and the switching element S13.

  Here, as in the case of FIG. 4 described above, the operation of the power distribution circuit 1 in the steady operation state is performed in one cycle of the change of the current It1 flowing in the winding L1 of the transformer T (current It2 flowing in the winding L2). Is divided into six sections of STEP1 to STEP6.

  As shown in FIG. 11, STEP1 is a period from when the current It2 flowing through the winding L2 of the transformer T increases from 0 ampere until the switching elements S11 and S14 are turned on and the switching elements S12 and S13 are turned off.

  STEP2 is a period from the end of STEP1 until the switching elements S22 and S23 are turned on and the switching elements S21 and S24 are turned off. STEP3 is a period from the end of STEP2 until the current It2 decreases to 0 amperes.

  STEP4 is a period from the end of STEP3 until the switching elements S11 and S14 are turned off and the switching elements S12 and S13 are turned on. STEP5 is a period from the end of STEP4 until the switching elements S21 and S24 are turned on and the switching elements S22 and S23 are turned off.

  STEP6 is a period from the end of STEP5 until the current It2 flowing in the opposite direction decreases to 0 ampere. In STEP 6 and subsequent steps, the operation is repeated from STEP 1 again.

  In STEP1 of FIG. 11, the switching elements S21 and S24 are ON, the current It2 monotonously increases in the forward direction, and the current It1 monotonously increases in the reverse direction. In STEP1 of the figure, as shown in FIG. 12, the current Ib flows into the charge / discharge path 4 from the positive terminal P1 of the solar cell M2 through the connection point j3.

A part of the current Ib is shunted from the connection point j19 to the capacitor C2 as the current Id and charged, and the rest is supplied as the current It2 from the charging / discharging path 4 side via the connection point j9. It flows through the line L2, and further flows from the connection point j12 to the charge / discharge path 5 side.

  In STEP 1, the current It 2 that has passed through the winding L 2 merges with the current Id flowing through the capacitor C 2 at the connection point j 20 to become the current Ib and flows through the charging / discharging path 5, and from the connection point j 4 via the output circuit A. Flows to the negative terminal P2 of the solar cell M2.

  On the other hand, since the switching elements S12 and S13 are ON, as shown in FIG. 11, a current It1 that increases in the opposite direction to the current It2 is induced in the other winding L1 of the transformer T. This current It1 flows through the winding L1 from the charge / discharge path 2 side via the connection point j7, and further flows from the connection point j6 to the charge / discharge path 3 side.

  In STEP 1, the capacitor C 1 is discharged, and the discharge current Ic is divided into a current It 1 flowing to the winding L 1 and a current Ia flowing through the charge / discharge path 2 at a connection point j 17 with the charge / discharge path 2. The current Ia is added to the output current of the solar cell M1 at the connection point j1 and flows to the external load via the output electric circuit A.

  On the other hand, a part of the output current of the solar cell M2 is shunted from the connection point j2 with the connection circuit B into the charge / discharge path 3 and flows into the current Ia, and merges with the current It1 at the connection point j18. And flows to the capacitor C1.

  As shown in FIG. 13, in STEP2, the switching elements S21 and S24 are ON, the switching elements S22 and S23 are OFF, and the charging / discharging path 4 has a connection point j3 from the positive terminal P1 of the solar cell M2 to the connecting circuit B. The current Ib flows in via the connection point, merges with the discharge current Id of the capacitor C2 at the connection point j19, and flows into the winding L2 as the current It2.

  The current It2 further flows into the charging / discharging path 5 at the connection point j12, is shunted at the connection point j20, part of which flows as the current Id to the capacitor C2, and the rest as the current Ib from the connection point j4 to the output circuit A. To the negative terminal P2 of the solar cell M2. Note that, as shown in FIG. 11, in STEP2, the current It2 gradually decreases.

  On the other hand, in STEP2, the switching elements S11 and S14 are ON, and the switching elements S12 and S13 are OFF. As shown in FIG. 13, a current It1 is induced in the winding L1 in the direction opposite to the current It2.

  This current It1 flows through the charging / discharging path 2 from the connection point j5, and a part of the current It1 flows into the capacitor C1 as the current Ic and charges it, and the rest is the current Ia as the solar cell M1 at the connection point j1. To the external load via the output electric circuit A.

  On the other hand, the current Ia flows into the charging / discharging path 3 from the solar cell M2 side via the connection point j2 with the connection electric path B. The current Ia is added with the current Ic flowing through the capacitor C1 at the connection point j18 and flows to the winding L1 as the current It1.

  Next, in STEP3, the switching elements S22 and S23 are ON, the switching elements S21 and S24 are OFF, and the current It2 flows in the winding L2 in a forward direction as shown in FIG.

  As shown in FIG. 14, the current It2 flows from the charge / discharge path 5 side via the connection point j10 through the winding L2 to the charge / discharge path 4 side via the connection point j11. Is connected to the current Ib flowing into the charge / discharge path 4 from the positive terminal P1 of the solar cell M2 via the connection point j3, and flows into the capacitor C2 as the current Id to be charged.

  The current Id is further shunted into a current It2 that is directed to the winding L2 at the connection point j20 and a current Ib that flows from the charge / discharge path 5 to the negative terminal P2 of the solar cell M2 via the output circuit A at the connection point j4.

  In STEP 3, the switching elements S11 and S14 are ON and the switching elements S12 and S13 are OFF, and the current It1 induced in the winding L1 flows in the reverse direction while decreasing as shown in FIG.

  The current It1 flows from the charge / discharge path 3 side via the connection point j8 through the winding L1 to the charge / discharge path 2 side via the connection point j5, and is discharged from the capacitor C1 at the connection point j17. The current Ia is merged with Ic to be added to the current flowing through the solar cell M1 from the charging / discharging path 2 at the connection point j1, and flows to the external load via the output electric path A.

  On the other hand, in the charging / discharging path 3, a part of the current flowing from the solar cell M2 side to the solar cell M1 side through the connection circuit B flows as the current Ia from the connection point j2 and flows to the capacitor C1 at the connection point j18. The current is split into the current It1 flowing to the winding L1.

  In STEP4, the switching elements S22 and S23 are ON, and the switching elements S21 and S24 are OFF. As shown in FIG. 15, the current It2 reverses the winding L2 via the connection point j11 from the charge / discharge path 4 side. In the direction and further from the connection point j10 to the charge / discharge path 5 side.

  Further, the switching elements S11 and S14 are ON, the switching elements S12 and S13 are OFF, and the current It1 induced in the winding L1 is forward from the charging / discharging path 2 via the connection point j5. And further flows from the connection point j8 to the charge / discharge path 3 side.

  As shown in FIG. 11, in STEP 4, the direction of the current It1 with respect to the winding L1 and the direction of the current It2 with respect to the winding L2 are opposite to those in STEP1, but the other current flows are the same as in STEP1. is there.

  In STEP5, the switching elements S21 and S24 are OFF and the switching elements S22 and S23 are ON. As shown in FIG. 16, the current It2 reverses the winding L2 from the charge / discharge path 4 via the connection point j11. In the direction and further from the connection point j10 to the charge / discharge path 5 side.

  Further, the switching elements S11 and S14 are OFF, the switching elements S12 and S13 are ON, and the current It1 induced in the winding L1 flows forward through the winding L1 via the connection point j6 from the charge / discharge path 3 side. And further flows from the connection point j7 to the charge / discharge path 3 side.

  As shown in FIG. 11, in STEP5, the direction of the current It1 with respect to the winding L1 and the direction of the current It2 with respect to the winding L2 are opposite to those in STEP2, but the other current flows are the same as in STEP2. is there.

  In STEP6, the switching elements S21 and S24 are ON, and the switching elements S22 and S23 are OFF. As shown in FIG. 17, the current It2 flows in the reverse direction through the winding L2 via the connection point j12 from the charge / discharge path 5 side. And then flows from the connection point j9 to the charge / discharge path 4 side.

  Further, the switching elements S11 and S14 are OFF, the switching elements S12 and S13 are ON, and the current It1 induced in the winding L1 flows forward through the winding L1 via the connection point j6 from the charge / discharge path 3 side. And further flows from the connection point j7 to the charge / discharge path 2 side.

  As shown in FIG. 11, in STEP 6, the direction of the current It1 with respect to the winding L1 and the direction of the current It2 with respect to the winding L2 are opposite to those in STEP3, but the other current flows are the same as in STEP3. is there.

  As described above, when the generated power of the rear-stage solar cell M2 is larger than the power generation output of the front-stage solar cell M1, the current Ia flowing through the charge / discharge path 2 of the power distribution circuit 1 is as shown in STEP1 to STEP6. Since it is added to the output current of the solar cell M1 in each period, the power generation efficiency of the system is improved as in the case where the generated power of the preceding solar cell M1 is larger than the generated output of the subsequent solar cell M2. .

  The power distribution circuit 1 of the present invention is a solar system that has a difference in power generation output by applying the operating principle of a DAB (Dual Active Bridge) type bidirectional DC-DC converter in which full-bridge switching elements are provided on both sides of a transformer. Electric power is distributed between the battery M1 and the solar battery M2.

  The DC-DC converter includes four switching elements S11 to S14 and four switching element bridges and capacitors corresponding to the capacitor C1, and four switching elements S21 to S24 and a capacitor C2 in the power distribution circuit 1 shown in FIG. 4 switching element bridges and capacitors respectively corresponding to, and the input direct current is converted into alternating current by the input side capacitor and the four switching element bridges, and supplied to the transformer primary winding, The operation of converting the alternating current induced in the secondary winding to direct current again by the bridge of the output side capacitor and the four switching elements is performed.

In such a DC-DC converter, the electric power P moving from the input side to the output side via the transformer has the input voltage V1, the output voltage V2, the switching angular frequency ω, the leakage inductance of the transformer and the Ls. Is given by the following equation (1).
P = (V1V2 / ωLs) · δ (1-δ / π) (1)

  Here, δ is a phase angle representing a timing shift of the switching operation between the bridge of the input side switching element and the bridge of the output side switching element, and the input side is advanced by the phase angle δ with respect to the output side. doing. Note that 0 <δ <π.

  Therefore, in the power distribution circuit 1 shown in FIG. 1, the output voltage of the solar cell M1 detected by the voltage sensor VS1 is V1, the output voltage of the solar cell M2 detected by the voltage sensor VS2 is V2, and the leakage of the transformer T The inductance generation side Ls and the angular frequency of the pulse signal output by the pulse oscillator of the switching control circuit 10 shown in FIG. The mobile power P distributed to the smaller side is calculated by the above equation (1).

  FIG. 18 is a graph showing the relationship between the mobile power P and the phase angle δ in the power distribution circuit 1. As shown in the figure, the mobile power P is 0 when δ = 0 and π. If V1 and V2 are constant values, the above equation (1) indicates that the moving power P becomes the maximum value when δ = π / 2.

  However, these voltages V1 and V2 change according to changes in the maximum output operating point of the system as shown in FIG. 3 when the mobile power P is generated by the operation of the power distribution circuit 1, so that the voltage V1 , V2 change depending on the phase angle δ.

  Therefore, the calculation unit of the switching control circuit 10 periodically measures these voltages V1 and V2 by the voltage sensors VS1 and VS2 and controls the phase angle δ so that the moving power P becomes the maximum value.

  FIG. 19 is a diagram showing an operation flow of the switching control circuit 10. As shown in FIG. 19, when the circuit is activated, all the switching elements S11 to S24 shown in FIG. 1 are reset to OFF (A1).

  Next, the voltages V1 and V2 are measured (A2), and it is determined whether or not they are equal (A3). If they are equal, the two solar cells M1 and M2 have no difference in power generation output. In this case, after starting the timer (A4) and waiting for a predetermined time, the process is restarted from (A1).

  If not equal, it is next determined whether or not the voltage V1 is greater than the voltage V2 (A5). If the voltage V1 is greater than the voltage V2, the switching element S11 on the solar cell M1 side is connected. The timing of periodic ON / OFF operation of the switching element group consisting of the group of the switching element S14 and the group of the switching element S12 and the switching element S13, the group of the switching element S21 and the switching element 24 on the solar cell M2 side, The phase angle δ is advanced by π = π / 2 with respect to the switching element group including the pair of the switching element 22 and the switching element S23 (A6).

  When the voltage V1 is smaller than the voltage V2, the switching element S21 and the switching element 24 on the solar cell M2 side, and the switching element group including the switching element 22 and the switching element S23 are periodically turned on. The timing of the / OFF operation is the phase angle δ = π / 2 with respect to the switching element group consisting of the combination of the switching element S11 and the switching element S14 and the combination of the switching element S12 and the switching element S13 on the solar cell M1 side. Advance (A7).

  Next, a minute angle Δδ is added to δ to obtain δ1 (A8), and the voltages V1 and V2 are measured while the power distribution circuit 1 is operated at the phase angle δ1 (A9). Next, the phase angle δ1 and the voltage values V1 and V2 measured here are substituted into the equation (1), and the moving power at this time is calculated as P1 (A10).

  Next, a minute angle Δδ is subtracted from δ to obtain δ2 (A11), and the voltages V1 and V2 are measured while operating the power distribution circuit 1 at the phase angle δ2 (A12). Next, the phase angle δ2 and the voltage values V1 and V2 measured here are substituted into the equation (1), and the moving power at this time is calculated as P2 (A13).

  Next, it is determined whether or not the two mobile powers P1 and P2 are equal (A14). If they are equal, the phase angle is set to δ (A15) and the time set by the timer (A4) is set. After continuing the switching operation, (A1) and subsequent steps are repeatedly executed.

  On the other hand, if the mobile power P1 is not equal, it is determined whether or not the mobile power P1 is greater than the mobile power P2 (A16). If the mobile power P1 is greater than the mobile power P2, the previous procedure (A8) is performed in (A17). ) Is set as δ, and the procedure from (A8) onward is executed again. When P1 is smaller than P2, in (A18), δ2 set in the previous procedure (A11) is set to δ, and the procedure after (A8) is executed again.

  As described above, in the power distribution circuit 1 of the present embodiment, the mobile power P distributed between the two solar cells M1 and M2 from the larger power generation output side to the smaller power generation circuit 1 via the power distribution circuit 1. The value of the phase angle δ is controlled so that is always the maximum.

  As shown in FIG. 3, the output voltages V1b of the solar cells M1 and M2 corresponding to the maximum output operating point P′m when the power distribution circuit 1 is operating at the phase angle δ at which the moving power P is maximized. , V2b does not change significantly with respect to the output voltages V1a, V2a corresponding to the maximum output operating point Pm when the power distribution circuit 1 is not operated.

  Therefore, the changes in the voltages V1 and V2 due to the change in the phase angle δ are relatively small, and the change in the moving power P calculated by the above-described equation (1) is δ (1-δ / π) in the equation. It is considered that it is greatly influenced, and as shown in FIG. 18, the moving power P becomes maximum in the vicinity of the phase angle δ = π / 2.

  Therefore, although the power generation efficiency slightly decreases, in FIG. 19, after executing the procedure (A6) or (A7), the processing after (A8) is omitted, and the processing from (A1) is repeated through (A4). You may do it.

  Next, FIG. 20 is a schematic diagram of a photovoltaic power generation system including three solar cells M1, M2, and M3 connected in series, showing another embodiment of the power distribution circuit of the present invention. As shown, the positive terminal P1 of the solar cell M1 and the negative terminal P2 of the solar cell M3 are connected to an external load via the output electric circuit A.

  Further, between the negative electrode terminal P2 of the solar cell M1 and the positive electrode terminal P1 of the solar cell M2, and between the negative electrode terminal P2 of the solar cell M2 and the positive electrode terminal P1 of the solar cell M3, the connection electric circuit B and the connection electric circuit B, respectively. Connected with '. Further, bypass diodes BD1, BD2, and BD3 are connected between the positive terminal P1 and the negative terminal P2 of the solar cells M1, M2, and M3, respectively.

  In this system, the same circuit as the power distribution circuit 1 of FIG. 1 described above is incorporated between the solar cells M1 and M2 and the solar cells M2 and M3 which are adjacent to each other in the front and rear.

  Moreover, in each embodiment mentioned above, although the system which connected two solar cells M1 and M2 in series and the system which connected three solar cells M1, M2, and M3 in series were demonstrated, this invention is these implementation. The present invention is not limited to the form, and can be applied to a photovoltaic power generation system in which four or more solar cells are connected in series.

  The power distribution circuit for solar cells according to the present invention can be effectively used to improve the decrease in power generation efficiency of solar cell modules and clusters due to the shade of the solar power generation system. In addition, solar power generation systems that combine different types of solar cell modules, solar power generation systems in which multiple solar cell modules including flexible solar cells are installed in different directions, and tracking concentrating type A system with different output characteristics of individual solar cells depending on the light collection characteristics of the condenser lens, such as a high-efficiency solar power generation system, a system with a double-sided solar cell module that also receives sunlight from the back surface, etc. In various cases, it can also be used as a means for increasing power generation efficiency.

  In addition, the power distribution circuit for solar cells of the present invention can be used to improve power generation efficiency when the output characteristics between solar cells vary due to deterioration over time or contamination of the light receiving surface in an existing solar power generation system. It is.

DESCRIPTION OF SYMBOLS 1 Electric power distribution circuit 2 Charging / discharging path (1st charging / discharging path)
3 charge / discharge paths (second charge / discharge paths)
4 Charging / discharging path (third charging / discharging path)
5 Charging / discharging path (fourth charging / discharging path)
6 communication circuit (first communication circuit)
7 communication circuit (second communication circuit)
8 communication circuit (third communication circuit)
9 Connection circuit (fourth connection circuit)
10 Switching control circuit A Output circuit B, B 'Connection circuit
BD1, BD2, BD3 Bypass diode C1 Capacitor (first capacitor)
C2 capacitor (second capacitor)
J1-J24 connection point
M1, M2, M3 Solar cell module T transformer L1 winding (first winding)
L2 winding (second winding)
S11 Switching element (first switching element)
S12 Switching element (second switching element)
S13 Switching element (third switching element)
S14 Switching element (fourth switching element)
S21 Switching element (fifth switching element)
S22 Switching element (sixth switching element)
S23 Switching element (seventh switching element)
S24 Switching element (eighth switching element)
VS1 voltage sensor (first voltage sensor)
VS2 voltage sensor (second voltage sensor)
LPF1, LPF2 Low pass filter

Claims (2)

Each of the power distribution circuits provided between the front and rear adjacent solar cells connected in parallel with a plurality of bypass diodes and connected in series with an external load,
A first charge / discharge path that is electrically connected to the positive electrode terminal of the preceding solar cell;
A second charge / discharge path electrically connected to the negative terminal of the solar cell in the previous stage;
A third charge / discharge path electrically connected to the positive electrode terminal of the subsequent solar cell;
A fourth charge / discharge path electrically connected to the negative terminal of the subsequent solar cell;
A first communication circuit having one end connected to the first charge / discharge path and the other end connected to the second charge / discharge path;
A second communication circuit having one end connected to the first charge / discharge path and the other end connected to the second charge / discharge path;
A third communication circuit having one end connected to the third charge / discharge path and the other end connected to the fourth charge / discharge path;
A fourth communication circuit having one end connected to the third charge / discharge path and the other end connected to the fourth charge / discharge path;
A first switching element incorporated in the first communication circuit adjacent to the connection point with the first charge / discharge path;
A second switching element incorporated in the first communication circuit adjacent to the connection point with the second charge / discharge path;
A third switching element incorporated in the second communication circuit next to the connection point with the first charge / discharge path;
A fourth switching element incorporated in the second communication circuit next to the connection point with the second charge / discharge path;
A fifth switching element incorporated in the third communication circuit adjacent to the connection point with the third charge / discharge path;
A sixth switching element incorporated in the third communication circuit adjacent to the connection point with the fourth charge / discharge path;
A seventh switching element incorporated in the fourth communication circuit next to the connection point with the third charge / discharge path;
An eighth switching element incorporated in the fourth communication circuit next to the connection point with the fourth charge / discharge path;
One end is connected to the first connecting circuit between the first switching element and the second switching element, and the other end is connected to the second connecting circuit between the third switching element and the fourth switching element. A first winding connected to the first winding and magnetically coupled to the winding, and one end is connected to the third communication circuit between the fifth switching element and the sixth switching element, A transformer having a winding ratio of 1: 1, the second end having a second winding connected to the fourth connecting circuit between the seventh switching element and the eighth switching element;
A first capacitor connected across the first charge / discharge path and the second charge / discharge path;
A second capacitor connected across the third charge / discharge path and the fourth charge / discharge path;
A first voltage sensor for detecting the output voltage of the solar cell in the previous stage;
A second voltage sensor for detecting the output voltage of the solar cell in the latter stage;
A switching control circuit that repeats ON / OFF operations of the respective switching elements at a common cycle,
In the switching control circuit, the first and fourth switching element sets and the second and third switching element sets have the same phase in each set, and the opposite phases between these sets. The group of the fifth and eighth switching elements and the group of the sixth and seventh switching elements are operated in the same phase within each group, and each switching element is turned on / off with an opposite phase between these groups. With
When the detection value of the first voltage sensor is larger than the detection value of the second voltage sensor, a switching element group consisting of a set of first and fourth switching elements and a set of second and third switching elements The ON / OFF operation timing of the switching element group of the fifth and eighth switching elements and the ON / OFF operation timing of the switching element group consisting of the sixth and seventh switching elements is set to a predetermined phase angle δ ( However, the phase is advanced by 0 <δ <π)
When the detection value of the second voltage sensor is larger than the detection value of the first voltage sensor, a switching element group consisting of a set of fifth and eighth switching elements and a set of sixth and seventh switching elements The ON / OFF operation timing is set to a predetermined phase angle δ () than the ON / OFF operation timing of the switching element group including the first and fourth switching element sets and the second and third switching element sets. However, the solar cell power distribution circuit is characterized in that the phase is advanced by 0 <δ <π). The switching control circuit, based on the detection values of the first voltage sensor and the second voltage sensor, moves power transferred between the first winding and the second winding of the transformer represented by the following equation: The solar cell power distribution circuit according to claim 1, further comprising an arithmetic unit that calculates a phase angle δ at which P is maximized.
P = (V1V2 / ωLs) · δ (1-δ / π)
Here, V1 is the output voltage of the former solar cell detected by the first voltage sensor, V2 is the output voltage of the latter solar cell detected by the second voltage sensor, and ω is the output voltage of each switching element. The angular frequency of the ON / OFF operation, Ls, represents the leakage inductance of the transformer.

Images